15915331981 has 8 divisors (see below), whose sum is σ = 15943429880. Its totient is φ = 15887259648.

The previous prime is 15915331891. The next prime is 15915332003. The reversal of 15915331981 is 18913351951.

It can be written as a sum of positive squares in 4 ways, for example, as 710222500 + 15205109481 = 26650^2 + 123309^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 15915331981 - 2⁷ = 15915331853 is a prime.

It is a super-2 number, since 2×15915331981² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15915338981) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1558765 + ... + 1568941.

It is an arithmetic number, because the mean of its divisors is an integer number (1992928735).

Almost surely, 2^15915331981 is an apocalyptic number.

It is an amenable number.

15915331981 is a deficient number, since it is larger than the sum of its proper divisors (28097899).

15915331981 is a wasteful number, since it uses less digits than its factorization.

15915331981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12783.

The product of its digits is 145800, while the sum is 46.

The spelling of 15915331981 in words is "fifteen billion, nine hundred fifteen million, three hundred thirty-one thousand, nine hundred eighty-one".